Pathologic conditions associated with impacted third molars: A retrospective study of panoramic radiographs in a Southern Brazilian population

Abstract

Purpose: This study investigated the prevalence of developmental and acquired pathologic conditions associated with impacted third molars (3Ms) in a Southern Brazilian population and evaluated whether demographic and tooth characteristics were correlated with the presence of bone or tooth lesions.

Materials and methods: Panoramic radiographs were assessed for developmental (bone-related) or acquired (tooth-related) pathoses associated with impacted upper or lower 3Ms. Data on tooth positioning, tooth development, and patient demographics were collected. A trained, calibrated postgraduate student evaluated all images. Binary and multivariate logistic regression models were used to assess associations between outcomes and the demographic and radiographic variables. The threshold for statistical significance was set at 5% (P<0.05).

Results: The sample comprised panoramic radiographs from 2054 patients, predominantly female (59.2%), with a mean age of 27.2 ± 11.5 years. Overall, 4066 impacted 3Ms were evaluated, revealing 471 (11.6%) developmental and 710 (17.5%) acquired pathoses. Among the developmental pathoses, 460 (95.2%) were indicative of dentigerous cysts. Male sex, lower 3M location, vertical or distoangular positioning, and incomplete root formation were associated with an elevated likelihood of developmental pathology. Lower tooth position, complete root formation, and partial eruption were linked to an increased probability of an acquired pathology in the third or second molar.

Conclusion: The prevalence of pathologic conditions associated with impacted 3Ms was low. Male sex, lower 3M placement, horizontal or distoangular positioning, and incomplete root formation were associated with developmental pathoses, while lower tooth position, complete root formation, and partial eruption were related to acquired pathoses.

Keywords: Molar, Third; Radiography, Panoramic; Tooth, Extraction; Tooth, Impacted.

Fig. 1. Cropped panoramic radiographs show examples of impacted third molars (3Ms) organized by the Pell and Gregory classification. A: Class I. Sufficient space exists between the ramus and the distal portion of the second molar to accommodate the mesiodistal diameter of the 3M. B: Class II. The space between the second molar and the ramus of the mandible is less than the mesiodistal diameter of the 3M. C: Class III. The entirety or majority of the 3M is located within the ramus of the mandible. D: Position A. The occlusal plane of the impacted tooth aligns with the occlusal plane of the second molar. E: Position B. The occlusal plane of the impacted tooth is situated between the occlusal plane and the cervical line of the second molar. F: Position C. The impacted tooth is positioned below the cervical line of the second molar.

Fig. 2. Cropped panoramic radiographs illustrate examples of an impacted third molar, categorized according to the Winter classification system. A: Vertical angulation. B: Horizontal angulation. C: Distoangular angulation. D: Mesioangular angulation. E: Buccal angulation.

Fig. 3. Cropped panoramic radiographs display examples of impacted third molars at various Nolla stages. A: In stage 7, one-third of root formation is complete. B: In stage 8, two-thirds of root formation is complete. C: In Stage 9, the root formation is nearly complete, with the apex remaining open. D: In stage 10, root formation is complete.